This set of Strength of Materials Multiple Choice Questions & Answers (MCQs) focuses on “Sudden Loading”.

1. What is the relation between maximum stress induced due to sudden loading to maximum stress the gradual loading?

a) Maximum stress in sudden load is equal to the maximum stress in gradual load

b) Maximum stress in sudden load is half to the maximum stress in gradual load

c) Maximum stress in sudden load is twice to the maximum stress in gradual load

d) Maximum stress in sudden load is four times to the maximum stress in gradual load

View Answer

Explanation: Maximum stress in sudden loading = 2P/A

Maximum stress in gradual loading = P/A.

2. What is the strain energy stored in a body when the load is applied suddenly?

a) σE/V

b) σE^{2}/V

c) σV^{2}/E

d) σV^{2}/2E

View Answer

Explanation: Strain energy in gradual loading = σ

^{2}V/2E.

3. A tensile load of 60kN is suddenly applied to a circular bar of 4cm diameter. What will be the maximum instantaneous stress induced ?

a) 95.493 N/mm^{2}

b) 45.25 N/mm^{2}

c) 85.64 N/mm^{2}

d) 102.45 N/mm^{2}

View Answer

Explanation: Maximum instantaneous stress induced = 2P/A = 2×60000/400π = 95.49 N/mm

^{2}.

4. A tensile load of 60kN is suddenly applied to a circular bar of 4cm and 5m length. What will be the strain energy absorbed by the rod if E=2×105 N/mm^{2} ?

a) 140.5 N-m

b) 100 N-m

c) 197.45 N-m

d) 143.2 N-m

View Answer

Explanation: Maximum instantaneous stress induced = 2P/A = 2×60000/400π = 95.49 N/mm

^{2}

Strain energy = σ

^{2}V/2E = 95.492 x 2×106π / (2x2x105) = 143238 N-mm = 143.23 N-m.

5. A tensile load of 100kN is suddenly applied to a rectangular bar of dimension 2cmx4cm. What will be the instantaneous stress in bar?

a) 100 N/mm^{2}

b) 120 N/mm^{2}

c) 150 N/mm^{2}

d) 250 N/mm^{2}

View Answer

Explanation: Stress =2x load / area = 2×100,000/ (20×40) = 250 N/mm

^{2}.

6. 2 tensile load of 100kN is suddenly applied to a rectangular bar of dimension 2cmx4cm and length of 5m. What will be the strain energy absorbed in the bar if E=1×105 N/mm2 ?

a) 312.5 N-m

b) 314500 N-mm

c) 1250 N-m

d) 634 N-m

View Answer

Explanation: Stress = 2xload / area = 2×100,000/ (20×40) = 250 N/mm

^{2}

Strain energy = σ

^{2}V/2E = 250x250x20x40x5000/ (2×100,000) = 1250000 N-mm = 1250 N-m.

7. A steel rod is 2m long and 50mm in diameter. A axial pull of 100kN is suddenly applied to the rod. What will be the instantaneous stress induced in the rod ?

a) 101.89 N/mm^{2}

b) 94.25 N/mm^{2}

c) 130.45 N/mm^{2}

d) 178.63 N/mm^{2}

View Answer

Explanation: Area = π/4 d2 = 625π

Load = 100kN = 100×1000 N

Stress = 2 x load / area = 2x100x1000 / (625π ) = 101.86 N/mm

^{2}.

8. A steel rod is 2m long and 50mm in diameter. A axial pull of 100kN is suddenly applied to the rod. What will be the instantaneous elongation produced in the rod if E=22GN/m2?

a) 0.0097 mm

b) 1.0754 mm

c) 1.6354 mm

d) 1.0186 mm

View Answer

Explanation: Area = π/4 d2 = 625π

Load = 100kN = 100×1000 N

E=22GN/m

^{2}= 200 x 109 / 106 = 200,000 N/mm

^{2}

Stress = 2 x load / area = 2x100x1000 / (625 π )

Elongation = stress x length / E = 101.86×2000 / 200000 = 1.0186 mm.

9. What will be the amount of axial pull be applied on a a 4cm diameter bar to get an instantaneous stress value of 143 N/mm^{2} ?

a) 50kN

b) 60kN

c) 70kN

d) 80kN

View Answer

Explanation: Instantaneous stress = 2 x load / area

Load = instantaneous stress x area / 2

= 143 x 400×3.14 / 2 = 60kN.

10. What will be the instantaneous stress produced in a bar 10cm^{2} in area ans 4m long by the sudden application of tensile load of unknown magnitude, if the extension of the bar due to suddenly applied load is 1.35mm if E = 2×105 N/mm^{2} ?

a) 67.5 N/mm^{2}

b) 47 N/mm^{2}

c) 55.4 N/mm^{2}

d) 78.5 N/mm^{2}

View Answer

Explanation: The value of stress = load / area where area is 10cm

^{2}and load can be calculated by stress strain equation.

**Sanfoundry Global Education & Learning Series – Strength of Materials. **

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